When I was a mathematics graduate student, a mathematical physicist described to me the difference between mathematical physics and theoretical physics roughly as follows. The mathematical physicist is a mathematician who re-does the work of the theoretical physicist, about 10-15 years later, but with full mathematical rigor. So, wanting to make sure that all the mathematics is precise and right comes at the cost of being behind the state of the art. The theoretical physicist, typically, does not worry about rigor. She makes approximations as needed, assumes as needed that differential equations have solutions (after all, if they describe a physical situation, how can they not, she might—fallaciously[note 1]—ask?), and so on. The mathematical physicist is worried about all the assumptions, wanting them all to be laid out on the table. The physicist does not worry. And typically the physicist is right not to worry—her physicist's intuition, or whatever, is sufficiently reliable in the appropriate area, and she knows what area is appropriate.
I wonder if there isn't a similar relationship between the theologian and the philosophical theologian (at least of the analytic variety). For instance, the theologian may not worry about cashing out details of metaphors. She might talk about the Church as the body of Christ without wondering whether this means that the Church is a substance. She can talk about forgiveness without wondering about its metaphysics (a fascinating question for a later post). Of course, she also can ask whether the Church is a substance, and wonder about the metaphysics of forgiveness. But the point is that she doesn't have to. Likewise, the theoretical physicist presumably can stop and be utterly rigorous, and sometimes she does, but much of the time she doesn't and doesn't have to. But the philosophical theologian wants to get as clear as we can on what is behind the metaphor, eschewing metaphorical language as much as possible. She wants to be able to formulate the theological theses as rigorously as possible. And there is a price to be paid for this rigor, much higher than the price for mathematical physics which was just being behind. Many aspects of Revelation are, likely, essentially metaphorical in the sense that there is no non-metaphorical way of putting them without loss. So insisting on putting things more rigorously, she is not able to say much of what her theologian colleague can. But the work of the philosophical theologian is valuable, just like that of the mathematical physicist.